Month: October 2010

My first Android app is in the market place! Built with Adobe AIR, unBrix Alpha is a quick take on the classic breakout style game. This is more of a “lite” game at this point (hence the “Alpha” suffix), but it is already more complete than many of the other Arkanoid clones in iOS App Store. There also seems to be some last minute performance problems on the Android version. :-/ I guess that’s what I get for only testing on an iPhone for most of the development. I’ll have fixes to that soon. I’m pretty sure it’s related to the scaleMode I set in Flash – the problem is if I set that the faster mode – NO_SCALE – it’s way too small on most Android devices. I’ll probably need to add some manual sizing based on measurement. Of course non of this was needed on the iPhone version.

Download unBrix Alpha and let me know what you think! I’d provide a link, but I don’t know how.

Update: I Nerfed the framerate a bit to get it to run a little smoother. I think the problem will be solved better by setting NO_SCALE, but I’ll have to do that another time (probably when I get to iPad port!). I also fixed the red line, and the icon too (I don’t know that didn’t show up last time). There is a report of the paddle jumping to one side when some users remove their finger from the screen. I haven’t been able to reproduce, but please let me know if this happens to you! Here is a link to unBrix Alpha on appbrain (it isn’t showing the update yet).

Update 2: I switched to CPU rendering, because it seems as though GPU rendering is just slower on Android devices than CPU rendering – at least in this kind of game. Anyway, this solved a lot of problems, including missing text and missing affects. I also had to set a fullScreenRect to match the original intended size of the game (iPhone 3Gs size). Doing these two things cleaned up most of the performance issues and graphics glitches. I’ll work on getting the remainder of the basics in place, like proper shutdowns – so this doesn’t run in the background like it does now (didn’t have to worry about that for iOS!).

Well, it’s only a tech demo at the moment. I’ve been playing with this Breakout like game for a while, trying to learn the ins and outs of Flash mobile development – particularly as it relates to performance. I now have the unBrix demo running at close to 60FPS (59.1) – smooth as silk.

This won’t run at 60FPS on Android Flash Player plugin in the browser (or Firefox on Mac!) – this post is about the iPhone build – but here’s the web version to look at anyway.

Here is a blurry video of the thing running as a native iPhone app on a 3GS (I smoothed out the choppy splash transition in a later build by setting the BG element with cacheAsBitmapMatrix):

The most important thing was to make sure GPU acceleration was working, and to learn what things will impact performance in that area.

It turns out, there are some important differences with how GPU accelerated Flash woks compared with the traditional software renderer. In the software Flash renderer keeping your display list shallow, and sparse (using addChild/removeChild a lot) or avoiding the display list completely (by writing to BitmapData – as the Flixel game engine does) is a key optimization for performance. This is how the exploding bunny video demo is done, and why it’s so fast.

My current theory is that on GPU accelerated content (even on desktop) the reverse is true. You want to avoid CPU/system RAM to GPU/video RAM updates as much as possible – which means avoiding BitmapData updates which cause the player to upload a new texture to the GPU VRAM with every update. Because I don’t have access to the internals of the Flash Player architecture, I can’t be sure, but I think the bottle neck comes from clogging up the lanes between the CPU and GPU, and all stressing all three areas of the rendering pipeline (CPU, GPU and the bus) as they juggle around objects in memory. The key observation this conclusion is based on is the large performance impact addChild and removeChild has on the framerate. So I relentlessly avoid that in my iPhone Flash development – I precache everything, and don’t mess with the display list. This is also one reason why filters (which operate on a BitmapData representation of the DisplayObject you apply them to) are not recommended on mobile content.

Anyway, hopefully I can turn this into a full app for iPhone in a reasonable timeframe. 🙂